1. Technical Field
The present invention relates in general to an improved data storage system and in particular to an improved method for accurately reading and storing data blocks within a data storage system. Still more particularly the present invention relates to an improved method and system for accurately identifying the end of each data block within a data storage system.
2. Description of the Related Art
Modern data processing systems often use digital signal recording devices attached to host processors to record records as addressable units within magnetic tape storage systems.
Examples of systems which may be utilized to record records within a magnetic tape storage system are disclosed within Milligan et al., U.S. Pat. No. 4,393,445; Milligan et al., U.S. Pat. No. 4,435,762; Videki II, U.S. Pat. No. 4,471,457; Cole et al., U.S. Pat. No. 4,603,382; Bauer et al., U.S. Pat. No. 4,423,480; and Fry et al., U.S. Pat. No. 4,403,286. Each of the aforementioned patents discloses a magnetic tape storage system which may be advantageously employed in carrying out the method and system of the present invention.
In such data storage systems, it is practically a necessity that each track of data within the recording medium includes multiple synchronization characters. Such synchronization characters are necessary so that the data may be considered self-synchronizing. Without such self-synchronizing, data may not be successfully recovered. This self-synchronizing is typically accomplished by inserting various synchronization characters between small blocks or sets of data signals so that the data stored therein may be accurately and efficiently recovered.
In modern data storage systems data are typically written to multiple tracks simultaneously. When such multiple track recording is utilized it is possible to determine various necessary parameters which may affect data recovery, even though individual track data within a group of multiple tracks may be lost. One such parameter is the location of the end of a particular block of data. It is imperative to accurately identify the end of a block of data in order to prevent errors which may occur due to overwriting data when additional data are appended to a record.
Systems which have been proposed to detect the end of a data block more reliably typically use a group of diverse synchronization characters which are positioned in a unique order within a data block, such that the end of a data block may be successfully located if these synchronization characters can be detected.
It should therefore be obvious that a need exists for a method and system whereby the location and identification of the end of a data block stored within a data processing system may be accurately accomplished. Such a system should be sufficiently robust such that variations in tape speed, poorly written data blocks, poorly written interblock gap characters, or damaged or defective data blocks will not result in an inability to detect the end of a data block within the data storage system.